Leaking Water Heater

Last updated September 24, 2026

A leaking water heater is one of the more urgent calls we get, and where the leak is coming from changes what it means and what happens next.

Where the water is actually coming from

Water at the base of the tank often means the tank itself has corroded through, not repairable. Water from a fitting, valve, or the temperature and pressure relief valve can be a smaller, separately fixable problem. Condensation on a cold tank in a humid space can also look like a leak without being one.

What to do right now

If you can safely reach the cold water supply valve to the tank, close it. Don't touch the T&P relief valve, don't attempt to drain the tank yourself, and don't touch gas or electrical connections. If you smell gas, leave and call your gas utility and emergency services from outside.

Why a basement leak is treated differently

A leaking tank in a finished basement can reach flooring, drywall and belongings quickly. That urgency is different from a garage or unfinished-basement leak, and worth mentioning when you call.

What happens next

A technician confirms where the water is actually coming from. If it is the tank itself, replacement is the only option; if it is a fitting or valve, that may be a straightforward repair.

Distinguishing a leak from normal drainage

Some units have a drain pan with its own drain line, water in that line isn't necessarily a leak from the tank itself. Knowing whether your unit has a pan helps the technician interpret what you're seeing.

Protecting the area while you wait for help

Moving anything valuable away from standing or dripping water, and laying down towels if it's safe to do so, can limit damage while you wait, without touching the unit's connections yourself.

If the Leak Turns Out to Be the Tank

When the leak is confirmed to be coming from the tank body itself, the conversation moves directly to replacement, see our replacement page for what that process involves, including removal of the old, leaking unit.

Finding Where the Water Is Coming From

Not every puddle under a water heater means the tank has failed. Start at the top: the cold inlet and hot outlet connections, the relief valve and its discharge pipe, and any anode or element ports. Then check the drain valve near the bottom. Condensation can also form on a gas tank's flue or on cold pipes in humid weather, and a nearby furnace humidifier, softener or AC condensate line can drip onto the floor. Drying everything with a towel and watching where fresh water appears is the simplest diagnostic.

Leaks That Can Be Fixed

Leaks at fittings, unions and flexible connectors can usually be fixed by tightening or replacing the part. A dripping drain valve can often be capped or replaced. A relief valve that drips may have debris on its seat or may be reacting to high pressure from thermal expansion, which an expansion tank solves. Element gaskets on electric tanks can be replaced. None of these require a new water heater.

Leaks That Mean Replacement

Water seeping from the tank body, under the jacket or from the bottom of the tank means the inner steel tank has corroded through. That can't be patched. The tank should be drained and replaced before the leak worsens; small seeps can become sudden failures without warning.

Relief Valve Discharges

If the relief valve is releasing a steady stream of hot water, the tank may be overheating or the pressure may be excessive. Turn off the gas or power, shut the cold supply and call for service. A thermostat failure that lets water overheat is a safety issue.

Protecting Finished Spaces

Many Colorado water heaters sit in finished basements or upstairs closets. A drain pan plumbed to a drain, a leak sensor and an automatic shutoff valve can limit damage from a future leak. Insurance claims for water damage are among the most common homeowner claims, and a water heater leak is a frequent cause.

What to Do Right Now

Close the cold-water valve on top of the heater, turn off gas or power, open a hot tap to relieve pressure and, if needed, drain the tank through a hose to a floor drain or outside.

A Typical Colorado Leak Call

A homeowner in Centennial finds water spreading across the finished basement carpet on a Sunday morning. The 50-gallon gas tank is fourteen years old. After shutting off the cold supply and gas, the technician drains the tank and finds the leak coming from beneath the jacket, meaning the inner tank has rusted through. A replacement is installed that afternoon with a drain pan plumbed to the floor drain, a leak sensor with an automatic shutoff valve and an expansion tank, since the home has a pressure-reducing valve. The homeowner files an insurance claim for the carpet with photos taken before cleanup.

Condensation That Looks Like a Leak

In Colorado's winter, when inlet water is very cold, a freshly filled gas tank can produce condensation inside the combustion chamber that drips onto the burner and the floor. It usually stops once the water warms up. If water keeps appearing after the tank is at temperature, it's a real leak.

Questions Homeowners Ask

Can a leaking tank be patched? No; the tank body must be replaced.

Will insurance cover damage? Often, for sudden leaks; less often for long-term seepage. Check your policy.

How fast can a replacement happen? Often the same or next day when a suitable unit is in stock.

Leaks From Above the Heater

Sometimes water found on top of or around a water heater is coming from something above it: a furnace humidifier, an air conditioning coil's condensate pan, a leaking pipe in the ceiling or roof flashing around the vent. Checking above the heater is part of any leak diagnosis.

Leaks at the Drain Valve

Plastic drain valves can crack or fail to seal, especially after a flush. A drain valve cap or a replacement brass valve fixes it.

After a Leak: Cleanup and Prevention

After a leak, dry the area thoroughly with fans and a dehumidifier to prevent mold, especially under carpet and drywall in finished basements. Check the base of nearby walls and any stored items. Once the water heater is replaced, adding a leak sensor with automatic shutoff and a drain pan plumbed to a drain helps prevent a repeat.

Leak Sensors

Battery leak sensors placed next to the water heater can alert you by sound or phone before a small leak becomes a big one.

Leak Timing

Leaks often start small at night when pressure peaks; check the base each morning if you suspect one.

Documenting a Leak

Before cleanup, take a few photos of where the water is, the tank's data plate and any wet flooring or drywall. Those details help the technician and any insurance claim.